The present invention relates, in general, to a safety arrangement for motor vehicles.
Side airbag systems are currently installed in motor vehicles to protect passengers in the event of a side impact collision or rollover. The side airbag systems are arranged in the area of the roof frame of the vehicle body and are inflated, when activated, by pressure gas released from a pressure gas source situated remote to the airbag. Supply of pressure gas to the side airbag system from a pressure gas source is realized through incorporation of lance-like fill pipes, which connect the pressure gas source with the airbag system and extend along the roof frame of the motor vehicle. The pressure gas may be arranged at various parts of the vehicle, in particular in the lower zone of the xe2x80x9cAxe2x80x9d pillar, xe2x80x9cBxe2x80x9d pillar or xe2x80x9cCxe2x80x9d or in the area of the wheel well, as described, for example, in German patent publication DE 197 58 024 A1. This publication also discloses the use of fill pipes of different configuration to extend substantially over the entire length of the vehicle, i.e., from the xe2x80x9cAxe2x80x9d pillar to the xe2x80x9cC/Dxe2x80x9d  pillar and in the lateral roof area of the motor vehicle.
Conventional side airbag systems suffer shortcomings because of the need for additional installation space to accommodate the fill pipes or connections between the pressure gas source and the air bag in the area of the roof frame. Moreover, the connections are exposed to great impact stress as the pressure gas source is activated. As a consequence, the connections require a minimum wall thickness. On the other hand, connections with greater wall thickness result in increased overall weight of the motor vehicle, so that fuel consumption is higher, accompanied by an adverse effect on the environment.
It would therefore be desirable and advantageous to provide an improved safety arrangement for motor vehicles which obviates prior art shortcomings and which exploits the advantages of a side airbag system while additionally enhancing the passive safety of passengers.
According to one aspect of the present invention, a safety arrangement for a motor vehicle includes an airbag, which is disposed in an area of a roof frame of a vehicle body including an xe2x80x9cAxe2x80x9d pillar, a xe2x80x9cBxe2x80x9d pillar, and a xe2x80x9cC/Dxe2x80x9d pillar, and a connecting tube coupled to the airbag and extending in the area of the roof frame from the xe2x80x9cAxe2x80x9d pillar to the xe2x80x9cC/Dxe2x80x9d pillar, wherein the connecting tube is configured to provide a stiffening for increasing a lateral rigidity of the roof frame and is firmly secured at least to the xe2x80x9cAxe2x80x9d pillar and the xe2x80x9cC/Dxe2x80x9d pillar.
The present invention resolves prior art problems by providing and so configuring the connecting tube as to assume two functions, namely, conduction of pressure gas to the airbag, and providing a stiffening effect of the roof frame. This dual function of the connecting tube significantly enhances the lateral rigidity of the roof frame. The increase in lateral rigidity in the roof frame zone may amount to about 15%.
The stiffening effect of the connecting tube is not only realized by the arrangement of the connecting tube in the roof frame area but also by the firm fixation of the ends of the connecting tube to the xe2x80x9cAxe2x80x9d pillar and the xe2x80x9cC/Dxe2x80x9d pillar. The fixation of the connecting tube to the xe2x80x9cAxe2x80x9d pillar and xe2x80x9cC/Dxe2x80x9d pillar provides an abutment for forces acting in the area of the roof frame.
A safety arrangement according to the present invention allows a simpler configuration of the roof frame through smaller sized cross sections while still realizing a constant stiffness, and thus compensation of the added weight as a consequence of the arrangement of the connecting tube. Thus, the airbag can be reliably supplied with pressure gas, while the stiffness in the roof area and the vehicle weight can be kept constant, without increase in the vehicle weight and accompanying adverse effects.
According to another feature of the present invention, the connecting tube may have at least one tube portion which, in the area of the xe2x80x9cAxe2x80x9d pillar and/or xe2x80x9cC/Dxe2x80x9d pillar, is in flat engagement with the xe2x80x9cAxe2x80x9d pillar and/or xe2x80x9cC/Dxe2x80x9d pillar. The flat engagement or even form-fitting contact of tube portions of the connecting tube upon the xe2x80x9cAxe2x80x9d pillar and/or xe2x80x9cC/Dxe2x80x9d pillar has the advantage that the connecting tube is prevented from buckling during rollover. In the event of rollover, generated forces normally act suddenly, so that a buckling of the connecting tube would prevent thrust forces to be absorbed by the xe2x80x9cAxe2x80x9d pillar. As a result, the connecting tube would contribute only minimally to an increase of the lateral rigidity in the roof area.
According to another feature of the present invention, there is provided a securement in a lower zone of the xe2x80x9cAxe2x80x9d pillar for form-fitting retention of the connecting tube. The form-fitting retention may be realized by providing a guide with a trough-like groove for receiving a portion of the connecting tube so as to counteract an undesired buckling of the connecting tube in longitudinal direction of the connecting tube and also in circumferential direction. Of course, the provision of a guide is optional in order to realize the form-fitting retention. Rather, it may be conceivable to configure the xe2x80x9cAxe2x80x9d pillar and the xe2x80x9cC/Dxe2x80x9d pillar in such a manner that, at least over predetermined portions, a form-fitting retention of the connecting tube is realized similar-to the previously described securement of the connecting tube via a guide.
According to another feature of the present invention, the connecting tube may have a bent configuration in conformity to a bent configuration of the securement, whereby a force acting in a longitudinal direction of the xe2x80x9cAxe2x80x9d pillar upon the connecting tube in a direction of the securement is introducible into the bent securement. This feature is based on the recognition that the force acting from the roof frame on the connecting tube can be introduced, in principle, through circumferential clamping of the connecting tube in the area of securement to the xe2x80x9cAxe2x80x9d pillar and the xe2x80x9cC/Dxe2x80x9d pillar as abutment. An bent securement and a complementary bent connecting tube have the added effect that the connecting tube cannot slip through the guide without plastic deformation. Through respective configuration of the securement in the area of the bent section, it is even possible to substantially omit the need for clamping elements because an impact stress can be absorbed solely by the bent section in the securement.
While the securement of the connecting tube to the xe2x80x9cAxe2x80x9d pillar and xe2x80x9cC/Dxe2x80x9d pillar significantly contributes to the functionality of the safety arrangement according to the present invention, it is also possible to provide a bracket for mounting the connecting tube in the area of the xe2x80x9cBxe2x80x9d pillar to the roof frame. In this way the lateral rigidity is further enhanced. In particular, the securement in the area of the xe2x80x9cBxe2x80x9d pillar prevents a relative movement of the connecting tube transversely to the traveling direction of the motor vehicle, and the tendency of the relatively long connecting tube to oscillate is suppressed.
According to another feature of the present invention, the connecting tube may have a forward tube portion, which extends from the xe2x80x9cAxe2x80x9d pillar to the xe2x80x9cBxe2x80x9d pillar, and rearward tube portion, which extends from the xe2x80x9cBxe2x80x9d pillar to the xe2x80x9cC/Dxe2x80x9d pillar, wherein both tube portions are linked together in the area of the xe2x80x9cBxe2x80x9d pillar. Of course, it is equally possible to configure the connecting tube of single-piece construction so as to extend from the xe2x80x9cAxe2x80x9d pillar to the xe2x80x9cC/Dxe2x80x9d pillar. In order to prevent a buckling of the connecting tube in the area of the xe2x80x9cBxe2x80x9d pillar, forward and rearward tube portions of the connecting tube are linked together in the area of the xe2x80x9cBxe2x80x9d pillar. The linkage need not necessarily be gas-permeable. It may also be conceivable to feed the forward tube portion from one gas pressure source, for example in the xe2x80x9cAxe2x80x9d pillar, and to feed the rearward tube portion of the connecting tube from a further gas pressure source, for example in the xe2x80x9cCxe2x80x9d pillar.
According to another feature of the present invention, there may be provided a bracket for securing the connecting tube in the area of the xe2x80x9cBxe2x80x9d pillar to the roof frame, wherein the forward tube portion has a trailing end and the rearward tube portion has a leading end, with the trailing end and the leading end being mounted by the bracket to the roof frame. The attachment of trailing and leading ends of the respective tube portions to the vehicle body removes a potential weak point at the joint between the neighboring ends of the tube portions.
Upon execution of a quasi static roof crushing test, in which the roof frame area of the motor vehicle, positioned on a fixed base, is loaded from outside at an angle of 25xc2x0 relative to the vertical, it has been shown that the lateral rigidity in the roof area can be increased up to 15% compared to a roof frame without tube.